Add Priti as an owner 🎉

@pritidesai has been a reviewer on many PRs (37 by the count at
https://github.com/tektoncd/pipeline/pulls?q=is%3Apr+is%3Aopen+reviewed-by%3Apritidesai)
and she has been the author of several PRs (27 at https://github.com/tektoncd/pipeline/pulls/pritidesai)
including finally (#2661) which was one of the most substantial changes
to pipeline execution since we implemented DAGs (not to mention that she
patiently worked with the evolution of this feature over several months
from the runOn feature which evolved into this one).

Thanks so much @pritidesai!!!! So excited that you want to become even
more involved in pipelines :D :D :D

OWNERS_ALIASES

@@ -7,6 +7,7 @@ aliases:
   - ImJasonH
   - sbwsg
   - vdemeester
+  - pritidesai
 
   apis-approvers:
   - afrittoli
@@ -16,6 +17,7 @@ aliases:
   - ImJasonH
   - sbwsg
   - vdemeester
+  - pritidesai
 
   productivity-approvers:
   - afrittoli